In many lighting applications the use of luminescent material in a remote configuration is suggested. Many luminescent materials, and more in particular organic phosphors, have a problem associated with photo-chemical stability. Especially organic phosphors deteriorate when being illuminated and when they are exposed to oxygen. In order to prevent fast deterioration of the material, a protection against oxygen is required. Thus, in order to guarantee a reasonable life time of a light source in which such luminescent materials are used, the luminescent material must be protected against oxygen.
Other luminescent materials, like quantum dots, are also sensitive for oxygen and detoriate under the influence of oxygen even without being illuminated.
In U.S. Pat. No. 7,839,072 a solution is proposed to protect organic phosphors against environmental air. The document discloses a translucent laminate sheet which includes at least one type of organic phosphor which is configured to convert light to another color and two light-transmitting members to seal the organic phosphor. The light-transmitting members are two parallel arranged plates and the organic phosphor is disposed to be held between then. At the circumference of the two plates, the opening between the two plates is hermetically sealed to prevent the deterioration of the organic phosphor under the influence of environmental air. The two plates are made of glass.
The translucent laminate sheet of the cited patent is a relative expensive solution for protecting the organic phosphors. The use of glass and the requirement to hermetically seal the opening between the glass plates at the circumference of the two plates result in a relatively expensive manufacturing process and the use of relatively expensive materials. Further, the use of glass results in a non-flexible configuration and the translucent laminate sheet has a flat shape.